March 16, 2016
Description
This is only one part from this: http://www.thingiverse.com/thing:620955
You will need the rest from there.
I printed the original but the tube that goes into the magazine wasn't long enough and didn't push the BB retaining pin in. I elongated that.
Edit: I changed the same thing on the updated part too, that's the M4_part2.stl
License:
Creative Commons - Attribution